1. Field of the Invention
This invention relates to predicting exhaust gas temperatures of an internal combustion engine.
2. Prior Art
Exhaust gas temperatures from internal combustion engines are typically considered when designing engine exhaust systems and components of such systems. Exhaust gas temperature from an engine can be determined by measuring the temperature of the engine exhaust gas. Alternatively, various thermodynamic considerations can be considered and a predicted exhaust gas temperature can be calculated based upon the thermal mass and conductance of the engine and the expected steady-state engine operating parameters.
It would be desirable to have a method of determining exhaust gas temperature as a function of actual engine operating conditions. The method can provide an engine control input for an engine controller which can adjust engine operation to control the engine exhaust gas temperature. Further, the accuracy of determining exhaust gas recirculation mass flow can be improved by using predicted exhaust gas temperature.
U.S. Pat. No. 4,656,829 teaches a method of predicting the temperature of the bed of a catalytic converter positioned in the exhaust system of an internal combustion engine. The catalytic converter temperature is predicted based on engine operating parameters by using empirically determined steady state temperature contributions to the catalytic converter from the mass air flow through the engine and the air/fuel ratio of the mixture supplied to the engine. These steady state values are applied to a first order lag filter equation having a time constant that is based on mass air flow through the engine and which defines the response of the catalytic converter temperature to transient operation of the engine. There is no specific compensation for engine speed, ignition timing and exhaust gas recirculation rate. Accordingly, a more accurate means for inferring and controlling engine exhaust gas temperature would be desirable.